Specific cyclooxygenase 2 inhibitor and anti-inflammatory agent

ABSTRACT

The invention relates to a specific cyclooxygenase 2 inhibitor which comprises, as an active ingredient, 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid represented by the following formula (1): ##STR1## or a salt thereof, as an anti-inflammatory agent. The compound specifically inhibits cyclooxygenase 2 without inhibiting cyclooxygenase 1 activity and thus it is low in toxicity and safe.

This application is a 371 of PCT/JP96/02583, filed Sept. 11, 1996.

TECHNICAL FIELD

The present invention relates to a specific cyclooxygenase 2 inhibitor and an anti-inflammatory agent.

BACKGROUND ART

Cyclooxygenase is an enzyme that catalyzes the addition of two oxygen molecules to arachidonic acid isolated from a phospholipid in a cell membrane by phospholipase A₂ to synthesize prostaglandin G₂, and is a rate-determining enzyme in the synthetic system of prostaglandins such as prostaglandin E₂ and thromboxane B₂. Since Vane reported in 1971 that non-steroidal anti-inflammatory drugs such as aspirin and indomethacin inhibit the cyclooxygenase activity to inhibit the production of prostaglandin E₂, thereby manifesting an anti-inflammatory effect, many non-steroidal anti-inflammatory drugs have been developed by pharmaceutical companies. However, most of the non-steroidal anti-inflammatory drugs inhibit the production of not only prostaglandin E₂ in an inflammatory site but also prostaglandin E₂ having a mucosa-protecting effect in digestive tracts, so that they have a stomach and intestine-damaging effect, and this side effect offers a clinical problem.

In recent years, it has been reported that subtype enzymes exist in the cyclooxygenase. Cyclooxygenase 1 conventionally known always manifests itself in cells of the gastric mucosa, seminal vesicle, platelet and the like and is considered to participate in the maintenance of homeostasis in the living body. On the other hand, cyclooxygenase 2 newly discovered is induced by stimulating a cell participating in inflammation such as a macrophage or synovial cell by a cytokine or the like and is hence considered to participate in an inflammatory reaction. The non-steroidal anti-inflammatory drugs clinically used at present are considered to inhibit not only cyclooxygenase 2 but also the cyclooxygenase 1 activity, thereby bringing about an anti-inflammatory effect and at the same time inducing gastrointestinal disorders.

Therefore, it is expected to develop a drug specifically inhibiting the cyclooxygenase 2 activity as a novel anti-inflammatory agent.

Accordingly, it is an object of the present invention to provide a drug which has an effect of specifically inhibiting the cyclooxygenase 2 activity, and an anti-inflammatory agent scarcely having a stomach and intestine-damaging effect.

DISCLOSURE OF THE INVENTION

In view of the foregoing circumstances, the present inventors have carried out an extensive investigation. As a result, it has been found that 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid or a salt thereof specifically inhibits cyclooxygenase 2, which catalyzes the synthesis of prostaglandin E₂ produced in an inflammatory site, without inhibiting the activity of cyclooxygenase 1 which catalyzes the synthesis of prostaglandin E₂ produced in the gastric mucosa or the like, and thus the use of this compound provides an excellent anti-inflammatory agent which scarcely causes any gastrointestinal disorders, thus leading to completion of the present invention.

According to the present invention, there is thus provided a specific cyclooxygenase 2 inhibitor which comprises, as an active ingredient, 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid represented by the following formula (1): ##STR2## or a salt thereof.

According to the present invention, there is also provided an anti-inflammatory agent which comprises, as an active ingredient, 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the formula (1) or a salt thereof.

According to the present invention, there is further provided a specific cyclooxygenase 2 inhibitor composition which comprises 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the formula (1) or a salt thereof and a pharmaceutically acceptable carrier.

According to the present invention, there is still further provided an anti-inflammatory agent composition which comprises 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the formula (1) or a salt thereof and a pharmaceutically acceptable carrier.

According to the present invention, there is yet still further provided use of 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid represented by the formula (1) or a salt thereof for the preparation of a specific cyclooxygenase 2 inhibitor.

According to the present invention, there is yet still further provided use of 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid represented by the formula (1) or a salt thereof for the preparation of an anti-inflammatory agent.

According to the present invention, there is yet still further provided a method of treating a disease caused by cyclooxygenase 2, which comprises administering an effective amount of 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the formula (1) or a salt thereof to a patient.

According to the present invention, there is yet still further provided a method of treating inflammation, which comprises administering an effective amount of 2-(2,6-dichloro-4-hydroxyanilino)phenylacetic acid represented by the formula (1) or a salt thereof to a patient.

BEST MODE FOR CARRYING OUT THE INVENTION

2-(2,6-Dichloro-4-hydroxyanilino)phenylacetic acid (hereinafter abbreviated as 4'-hydroxydiclofenac) represented by the formula (1) used in the specific cyclooxygenase 2 inhibitor according to the present invention is known as a main metabolite in blood of diclofenac. However, this compound (1) is not known at all to have an anti-inflammatory effect.

As a process for the preparation of 4'-hydroxy-diclofenac, there may be used any known process. The compound can be efficiently prepared, for example, in accordance with the following process: ##STR3##

More specifically, commercially available 2-aminobenzyl alcohol is N-acylated with a stoichiometric amount of benzoyl chloride into a benzoamide, and this product is then boiled under reflux in thionyl chloride to obtain an imidoyl chloride (1). The imidoyl chloride is then reacted with commercially available 2,6-dichloro-4-fluorophenol (2) to convert it into an imidate (3). The imidate is heated (for 30 minutes at 250° C.; Chapman rearrangement) without using any solvent to obtain a rearranged product (4). This compound (4) is converted into a cyanide (5) in accordance with a method known per se in the art, and the cyanide (5) is then hydrolyzed with a concentrated alkali. The hydrolyzate is neutralized, and is then isolated and purified by column chromatography on ODS.

The salt of 4'-hydroxydiclofenac is preferably an alkali metal salt, particularly, the sodium salt.

No particular limitation is imposed on the specific cyclooxygenase 2 inhibitor or anti-inflammatory agent according to the present invention. However, it is preferably used for a patient suffering from any of various inflammations such as chronic articular rheumatism.

When the specific cyclooxygenase 2 inhibitor or anti-inflammatory agent according to the present invention is administered to a patient, the preferable dose thereof varies according to the age and condition of the patient, and the like. However, it is preferably administered in a dose of generally 20 to 200 mg per day for an adult in terms of the active ingredient at once or in several portions. No particular limitation is imposed on the administration route thereof. Examples thereof include oral administration, injection administration and rectal administration.

The specific cyclooxygenase 2 inhibitor or anti-inflammatory agent according to the present invention includes the above-described 4'-hydroxydiclofenac or the salt thereof as an active ingredient and besides may contain any optional ingredients useful for the formulation of preparations, which are routinely used in medicinal compositions, in any suitable proportions. Examples of the optional ingredients include excipients, extending agents, binders, wetting agents, disintegrators, surfactants, lubricants, dispersing agents, buffers, preservatives, taste corrigents, perfume bases and coating agents.

Examples of preparation forms for the oral administration include powder, granules, tablets, sugarcoated tablets, capsules and ampoules, while examples of injection preparations include subcutaneous injections, intramusclar injections and intravenous injections.

EXAMPLES

The present invention will hereinafter be described more specifically by the following Examples which are included merely to illustrate the present invention, and do not limit the invention.

Example 1

(Specific Inhibitory Effect on Cyclooxygenase)

Added to 2 μl of a solution of 4'-hydroxydiclofenac, diclofenac or indomethacin dissolved in DMSO (dimethyl sulfoxide); end concentration: 0.01-100 μM! were 100 μl of a 50 mM tris-hydrochloric acid buffer solution (pH: 8.0) containing 1 mM epinephrine, 2 mM phenol, and 200 μg/ml of sheep seminal vesicle microsome (cyclooxygenase 1) or 5 units of cyclooxygenase 2, and the mixture was incubated at 37° C. for 5 minutes. After the incubation, 2 μl of a 5 mM solution of arachidonic acid (dissolved in ethanol) were added (end concentration: 100 μM), followed by incubation for additional 5 minutes. After the incubation for 5 minutes, 10 μl of a 22 mM solution of ferrous chloride were added, and the resultant mixture was cooled down to 0° C. to stop the reaction. After stopping the reaction, the reaction mixture was centrifuged at 10,000×g for 5 minutes to determine the amount of prostaglandin E₂ in the supernatant liquid thereof in accordance with the enzyme immunoassay. The cyclooxygenase-inhibiting effect of each test agent was determined by the average value of the amounts of prostaglandin E₂ produced, which were obtained by repeating the above process twice, and the amount of prostaglandin E₂ produced by using DMSO in place of the test agent to conduct the same treatment as described above. The percent inhibitions of cyclooxygenases 1 and 2 at the individual concentrations are shown in Table 1 and Table 2, respectively.

                  TABLE 1     ______________________________________     Percent inhibition of cyclooxygenase 1 (%)               0.01    0.1   1       10  100 (μM)     ______________________________________     4'-Hydroxydiclofenac                 0         0     13    3   15     Indomethacin                 15        30    40    55  85     Diclofenac  25        25    38    57  87     ______________________________________

                  TABLE 2     ______________________________________     Percent inhibition of cyclooxygenase 2 (%)               0.01    0.1   1       10  100 (μM)     ______________________________________     4'-Hydroxydiclofenac                 21        18    22    82  90     Indomethacin                 25        28    50    88  90     Diclofenac  20        40    80    88  90     ______________________________________

As apparent from Table 1 and Table 2, Inhibitory effects on cyclooxygenase 1 and cyclooxygenase 2 are recognized in indomethacin and diclofenac. On the other hand, no inhibitory effect on cyclooxygenase 1 is recognized in 4'-hydroxydiclofenac, and only an inhibitory effect on the cyclooxygenase 2 activity is recognized.

Example 2

(Effect of 4'-Hydroxydiclofenac on Production of Prostaglandin E₂ by Stimulation of Human Synovial Cell by IL-1β)

Synovial tissue obtained from a patient suffering from chronic articular rheumatism was placed in a Petri dish, cut and shredded, to which a 0.2% solution of collagenase was added. The mixture was left over for 2 hours under conditions of 5% CO₂ and 37° C. An equiamount of a 0.25% solution of trypsin was further added, and the resultant mixture was left over for 2 hours. After cells isolated were collected and centrifuged (170 ×g, 10 minutes) to remove the supernatant liquid thereof, a medium obtained by adding 10% FCS (fetal calf serum), 2 mM glutamine, 100 U/ml of penicillin, 100 μg/ml of streptomycin and 25 ng/ml of Fungizone to DMEM (Dulbecco modified minimum essential medium)! was added to the cells to wash them once. The cells were suspended in the medium, and the suspension was poured into a Petri dish and cultured under conditions of 5% CO₂ and 37° C. Cells adhered to the bottom of the Petri dish were provided as synovial cells. The cells (1×105 cells/ml) were poured in 1-ml portions into wells of a 24-well plate and cultured under conditions of 5% CO₂ and 37° C. After the cells were proliferated to an extent that they covered almost the entire surface of each well, the medium was changed to an SFM-101 medium (product of Nissui Seiyaku K.K.) containing 1% FCS. Added to an assigned well were 5 μl (end concentration: 0.001-100 μM) of a solution of 4'-hydroxydiclofenac, indomethacin or diclofenac. Furthermore, 10 μl (end concentration: 200 pg/ml) of a solution of IL-1βand 10 μl (end concentration: 10 μM) of arachidonic acid were added to conduct culture for 22 hours under conditions of 5% CO₂ and 37° C. After the culture, the supernatant liquid thereof was collected and filtered through a membrane filter (pore size: 0.22 μm, MILLIPORE), thereby determining the amount of prostaglandin E₂ in the filtrate in accordance with the enzyme immunoassay. The effect of each test agent on the production of prostaglandin E₂ by the human synovial cells was determined by the average value of the amounts of prostaglandin E₂ produced, which were obtained by repeating the above process 3 times, and the amount of prostaglandin E₂ produced by using DMSO in place of the test agent to conduct the same treatment as described above. The results are shown in Table 3.

                  TABLE 3     ______________________________________     Percent inhibition of prostaglandin E.sub.2 (%)                0.001                     0.01   0.1    1    10   100 (μM)     ______________________________________     4'-Hydroxydiclofenac                  -3     0      35   100  100  100     Indomethacin -3     5      62   100  100  100     Diclofenac   14     61     99   100  100  100     ______________________________________

As apparent from the results shown in Table 3, the inhibitory effect of 4'-hydroxydiclofenac on prostaglandin E₂ is almost comparable to indomethacin. It has been reported that in inflammation-related cells such as the synovial cell, the manifestation of cyclooxygenase 2 is induced by stimulating the cells by IL-1β without affecting the manifestation of cyclooxygenase 1. Therefore, 4'-hydroxydiclofenac is considered to inhibit cyclooxygenase 2 also in the cell-level test.

Referential Example

(Effect of 4'-Hydroxydiclofenac on Production of Thromboxane B₂ in Platelet)

Fresh blood adding 1 volume of ACD (acid-citrate dextrose; consisting of 65 mM citric acid, 85 mM sodium citrate and 110 mM glucose) to 9 volumes of the blood! collected from the heart of a rabbit under Nembutal anesthesia was centrifuged at 200 ×g for 10 minutes to collect the supernatant liquid thereof. The supernatant liquid was centrifuged at 700 ×g for 10 minutes, and precipitated platelets were suspended in an isotonic trishydrochloric acid buffer solution 50 mM tris(hydroxymethyl)aminomethane, 150 mM NaCl, 1 mM EDTA (ethylenediaminetetraacetic acid) and 5 mM glucose; pH: 7.2!. The suspension was further centrifuged at 700 ×g for 10 minutes and washed. After washed again, precipitated platelets were suspended in an isotonic HEPES (2- 4-(2-hydroxyethyl)-1-piperazinyl!ethane-sulfonic acid) buffer solution (10 mM HEPES, 145 mM NaCl, 5 mM KCl and 5.5 mM glucose; pH: 7.4) to adjust the concentration of the platelets to 3×10⁹ cells/ml. The thus-adjusted platelet suspension was poured in 1-ml portions into test tubes. To one of the test tubes, were added 5 Al (end concentration: 0.001-100 μM) of a solution of 4'-hydroxydiclofenac, indomethacin or diclofenac, and the test tube was preincubated for 30 minutes at 37° C. After the incubation, 10 μl (end concentration: 2 mM) of 200 mM CaCl₂ and 5 μl (end concentration: 5 μM) of 1 mM arachidonic acid were added, followed by incubation for additional 5 minutes. After the incubation, the test tube was transferred to an ice bath to stop the reaction. The test tube was centrifuged at 1,500 ×g and 4° C. for 10 minutes. After the supernatant liquid thereof was filtered through a membrane filter (pore size: 0.22 μm, MILLIPORE), the amount of thromboxane B₂ in the filtrate was determined in accordance with the enzyme immunoassay. The effect of each test agent on the production of thromboxane B₂ in the platelet was determined by the average value of the amounts of thromboxane B₂ produced, which were obtained by repeating the above process 3 times, and the amount of thromboxane B₂ produced by using DMSO in place of the test agent to conduct the same treatment as described above. The results are shown in Table 4.

                  TABLE 4     ______________________________________     Percent inhibition of thromboxane B.sub.2 (%)                0.001                     0.01    0.1   1    10  100 (μM)     ______________________________________     4'-Hydroxydiclofenac                  -25    -25     0   7    15  77     Indomethacin 2      50      76  77   78  78     Diclofenac   46     70      68  77   93  99     ______________________________________

As apparent from the results shown in Table 4, an inhibitory effect on the production of thromboxane B₂ is recognized in indomethacin and diclofenac. On the other hand, the inhibitory effect of 4'-hydroxydiclofenac is clearly weak compared with indomethacin. It has been known that thromboxane B₂ is produced in the platelet by the cyclooxygenase 1 activity. Therefore, the inhibitory effect of 4'hydroxydiclofenac on cyclooxygenase 1 is considered to be weak also in the cell-level test.

Example 3

The following ingredients were mixed, and the mixture was tableted.

                  TABLE 5     ______________________________________     4'-Hydroxydiclofenac   100    mg     Lactose                100    mg     Potato starch          39     mg     Microcrystalline cellulose                            30     mg     Synthetic aluminum silicate                            30     mg     Calcium stearate       1      mg     Total amount (per tablet)                            300    mg     ______________________________________

As described above, 4'-hydroxydiclofenac specifically inhibits cyclooxygenase 2, so that the use of this compound as an anti-inflammatory agent has an anti-inflammatory effect almost without causing any side effects such as gastrointestinal disorders.

Industrial Applicability

The specific cyclooxygenase 2 inhibitor according to the present invention specifically inhibits cyclooxygenase 2, which catalyzes the synthesis of prostaglandin E₂ produced in an inflammatory site, without inhibiting the activity of cyclooxygenase 1 which catalyzes the synthesis of prostaglandin E₂ produced in the gastric mucosa or the like.

Besides, the use of the anti-inflammatory agent comprising 4'-hydroxydiclofenac or the salt thereof as an active ingredient has an excellent anti-inflammatory effect without causing any gastrointestinal disorders as side effects. This agent is a main metabolite in blood of diclofenac which is already in clinical use as a non-steroidal anti-inflammatory agent, and is hence low in toxicity and safe. 

We claim:
 1. A method of treating a disease caused by cyclooxygenase 2, which comprises administering an effective amount of 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the following formula (1) ##STR4## or a salt thereof to a patient.
 2. A method of treating inflammation by inhibiting cyclooxygenase 2 activity without inhibiting activity of cyclooxygenase 1, which comprises administering an effective amount of 2-(2,6-dichloro-4-hydroxyanilino)-phenylacetic acid represented by the following formula (1) ##STR5## or a salt thereof to a patient. 